This invention relates to a method for reducing rub-off from a substrate, such as paper, having a toner image on at least one side of the substrate by depositing a plurality of dots of at least one phase change composition on the at least one side of the substrate bearing the image, said dots being one of colored or a combination of colored and clear (colorless) dots, said dots cumulatively covering an area of at least one side of the substrate bearing an image, said area being sufficient to reduce image rub-off from the substrate. This invention further relates to the use of color combinations or a combination of colored and clear phase change composition dots deposited on the toner images on a substrate to prevent rub-off from the substrate.
In electrophotographic copying processes, images are formed on selected substrates, typically paper, using small, dry, colored particles called toner. The thermoplastic toner is typically attached to a print substrate by a combination of heat and pressure using a fusing subassembly that partially melts the toner into the paper fibers at the surface of the paper substrate. Typically, in an electrophotographic printer, a heated fuser roller is used with a pressure roller to attach toner to a receiver and to control the surface image characteristics.
Fused toner images can be substantially abraded or xe2x80x9crubbed-offxe2x80x9d by processes such as duplex imaging, folding, sorting, stapling, binding, filing and the like. Residue from this abrasion process causes objectionable and undesirable marks on non-imaged areas of adjacent pages or covers. This process, and image quality defect, are known as xe2x80x9crub-offxe2x80x9d and exist to varying extents in many electrophotographic copies and prints. The basic xe2x80x9crequirementsxe2x80x9d for generation of rub-off are a donor (toner image), a receptor (adjacent paper page, envelope, mailing label, etc.), a differential velocity between donor and receptor, a load between donor and receptor and pressing them together. Toner rub-off may be reduced by the use of tougher toner, lower surface energy toner materials (resulting in lower coefficient of friction), better fused toner, and a smoother toner image surface finish (causing increased image gloss.) Unfortunately, as described in detail hereinafter, there are undesirable consequences associated with each of the above rub-off reduction factors. Extensive efforts have been directed to the development of improved methods for reducing rub-off without modification of the fusing process.
According to the present invention, rub-off from a substrate bearing a toner image is reduced by a method for reducing rub-off from a substrate having a front side and a back side and bearing a toner image on at least one of said sides, the method comprising: depositing at least one phase change composition on the at least one of the sides of the substrate which carries an image as a plurality of dots, the dots being one of colored dots, a combination of colored dots or a combination of colored and clear dots, and cumulatively covering an area of said image bearing side sufficient to reduce rub-off from said side.
The invention further relates to a method of reducing rub-off from a substrate having a front side and a back side and a plurality of printer, copier, or digital copier produced toner images on at least one of said sides, the method comprising: depositing on at least one image bearing side at least one phase change composition on at least a portion of the toner images as a plurality of dots, the dots being a combination of colored and clear dots, and cumulatively covering an area of the toner images sufficient to reduce rub-off from said side.